In thrust wedges with multiple weak layers, individual décollements are generally thought to control only the structural vergence of the thrust systems directly above them. However, along the strike of the Zagros Simply Folded Belt, the structures above a common basal décollement at the Hormuz salt layer exhibit different vergence, including forward-, doubly-, and backward-vergent thrust wedges. Despite the importance of intermediate décollements for determining structural styles in the Zagros Simply Folded Belt, their effects on the structural vergence of the thrust system beneath them remain poorly understood. To address this issue, we conducted systematic experiments using discrete element models with a basal décollement on top of the basement and an intermediate décollement within the overlying strata. By varying the strength, thickness, and depth of the intermediate décollement, we successfully reproduced all types of thrust wedges (i.e., forward-, doubly-, and backward-vergent) in the thrust system beneath it. This suggests that intermediate décollements can determine the vergence of the thrust wedges beneath them. Moreover, our results reveal that specific combinations of intermediate décollement properties and shortening rates are crucial for the development of a backward-vergent thrust wedge in the thrust system beneath the intermediate décollement. This provides an alternative mechanism for the formation of such wedges. Together with geological and geophysical observations, we propose that intermediate décollements are responsible for along-strike vergence variations in the Zagros Simply Folded Belt. Thus, the interactions between thrust systems at various scales should be emphasized.
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Research Article|
March 20, 2025
Early Publication
Discrete element modeling of the structural vergence beneath intermediate décollements: Implications for along-strike variations in the Zagros Simply Folded Belt
Chao Zhou;
Chao Zhou
1
State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China2
University of Chinese Academy of Sciences, Beijing 100049, China
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Jiankun He;
Jiankun He
1
State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China2
University of Chinese Academy of Sciences, Beijing 100049, China
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Hao Su;
Hao Su
3
Laboratory of Seismology and Physics of Earth’s Interior, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
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Jonas B. Ruh;
Jonas B. Ruh
4
Institute of Marine Sciences, Consejo Superior de Investigaciones Científicas, 08003, Barcelona, Spain
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Xun Wang;
Xun Wang
5
Key Laboratory of Earthquake Forecasting, Institute of Earthquake Forecasting, China Earthquake Administration, Beijing 100036, China
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Weimin Wang;
Weimin Wang
1
State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China
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Xinguo Wang;
Xinguo Wang
1
State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China
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Zhengyang Pan
Zhengyang Pan
5
Key Laboratory of Earthquake Forecasting, Institute of Earthquake Forecasting, China Earthquake Administration, Beijing 100036, China
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Chao Zhou
1
State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China2
University of Chinese Academy of Sciences, Beijing 100049, China
Jiankun He
1
State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China2
University of Chinese Academy of Sciences, Beijing 100049, China
Hao Su
3
Laboratory of Seismology and Physics of Earth’s Interior, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
Jonas B. Ruh
4
Institute of Marine Sciences, Consejo Superior de Investigaciones Científicas, 08003, Barcelona, Spain
Xun Wang
5
Key Laboratory of Earthquake Forecasting, Institute of Earthquake Forecasting, China Earthquake Administration, Beijing 100036, China
Weimin Wang
1
State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China
Xinguo Wang
1
State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China
Zhengyang Pan
5
Key Laboratory of Earthquake Forecasting, Institute of Earthquake Forecasting, China Earthquake Administration, Beijing 100036, China
Publisher: Geological Society of America
Received:
28 Aug 2024
Revision Received:
05 Jan 2025
Accepted:
01 Mar 2025
First Online:
21 Mar 2025
Online ISSN: 1943-2674
Print ISSN: 0016-7606
© 2025 Geological Society of America
GSA Bulletin (2025)
Article history
Received:
28 Aug 2024
Revision Received:
05 Jan 2025
Accepted:
01 Mar 2025
First Online:
21 Mar 2025
Citation
Chao Zhou, Jiankun He, Hao Su, Jonas B. Ruh, Xun Wang, Weimin Wang, Xinguo Wang, Zhengyang Pan; Discrete element modeling of the structural vergence beneath intermediate décollements: Implications for along-strike variations in the Zagros Simply Folded Belt. GSA Bulletin 2025; doi: https://doi.org/10.1130/B37988.1
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